The object of the invention is a process for the production of 4-acylamido-4,4-dicarbalkoxy-butanalphenylhydrazone by addition of an acylamidomalonic acid ester to acrolein in the presence of a catalyst and subsequent reaction of the 4-acylamido-4,4-dicarbalkoxybutanal with phenylhydrazine.
There are already known numerous processes for the production of 4-acylamido-4,4-dicarbalkoxybutanalphenylhydrazone, an important intermediate product in the synthesis of tryptophane by the Warner and Moe technique. They are differentiated essentially by the conditions in the Michael addition of the acylamidomalonic acid ester to acrolein:
In Moe et al., J. Amer. Chem. Soc. 70 (1948), 2763- 2765 there is described the Michael addition in the presence of sodium alcoholates. In the most favorable cases, use of benzene as the solvent and sodium methylate as the catalyst, the yield of phenylhydrazone is 87%.
In the Bull. Agr. Chem. Soc. Japan 21 (1957), 58 et seq. (cited in C.A. 51, 11451d), there is described the Michael addition in the presence of sodium methylate, sodium hydroxide, potassium hydroxide, potassium carbonate, sodium cyanide, barium hydroxide, di and triethylamine or basic ion exchange resins. The yields of phenylhydrazone amount to 60 to 77%.
In Novotny German Auslegeschrift 21 34 360 there is described the carrying out of the Michael addition in aqueous suspension in neutral or slightly alkaline suspension, the working example being carried out using sodium hydroxide. The yield of phenylhydrazone is stated to be quantitative, but there is formed a highly impure product.